Divide the following complex numbers: $\dfrac{10 e^{7\pi i / 12}}{ e^{3\pi i / 4}}$ (The dividend is plotted in blue and the divisor in plotted in green. Your current answer will be plotted orange.)
Solution: Dividing complex numbers in polar forms can be done by dividing the radii and subtracting the angles. The first number ( $10 e^{7\pi i / 12}$ ) has angle $\frac{7}{12}\pi$ and radius 10. The second number ( $ e^{3\pi i / 4}$ ) has angle $\frac{3}{4}\pi$ and radius 1. The radius of the result will be $\frac{10}{1}$ , which is 10. The difference of the angles is $\frac{7}{12}\pi - \frac{3}{4}\pi = -\frac{1}{6}\pi$ The angle $-\frac{1}{6}\pi$ is negative. A complex number goes a full circle if its angle is increased by $2 \pi$ , so it goes back to itself. Because of that, angles of complex numbers are convenient to keep between $0$ and $2 \pi$ $-\frac{1}{6}\pi + 2 \pi = \frac{11}{6}\pi$ The radius of the result is $10$ and the angle of the result is $\frac{11}{6}\pi$.